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Author Topic: Piston Rings or Valve Job  (Read 964 times)

BRADEY

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Piston Rings or Valve Job
« on: August 21, 2012, 07:30:08 AM »
How do I identify if my bike needs new set of piston rings or a valve job or both ? It's a 2003 Iron head 350 with 26000 miles, and has electronic CDI ignition. It has kind of lost its urge to pick up and mantain high speeds such as 55MPH which she could easily reach and do, all day long !

The bike is picking up oil way too sooner than she did earlier, and weirdly, she seems OK sometimes and then get backs to her lazy self again. I have checked the clutch plates, which seem to be ok. Just cant figure out, how can I get back the oomph ?

1 Thump

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Re: Piston Rings or Valve Job
« Reply #1 on: August 21, 2012, 08:40:42 PM »
Check your compression. Also check for carbon deposits in the head.

Arizoni

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Re: Piston Rings or Valve Job
« Reply #2 on: August 21, 2012, 09:07:11 PM »
Start with the basics.

Check the air filter.  Is it dirty?
Change the spark plug for a new one.
Have you cleaned the carburetor?  Perhaps a little Fuel Injector/Carburetor cleaner dumped into the fuel tank will open up a partially blocked jet.
Have you checked the throttle cable?  Sometimes these can stretch causing the throttle slide or throttle plate to not fully open.
Is the chain in good condition?  A neglected chain can rob horsepower that used to get to the ground.
Are the valves adjusted correctly?  If they are too loose it delays the valve timing.  If they are too tight the valves may be releasing compression and combustion gasses.

As was suggested, check the compression.  After getting a consistent reading, put a small amount of oil into the cylinder thru the spark plug hole.  Then run the test again.

If the compression is low and adding oil doesn't seem to fix it it indicates the valves are leaking.
If the compression is low and adding oil does seem to raise it, it indicates the piston rings are worn.
If the compression is high and the oil doesn't change it it indicates that all is well and you should be happy. :)
Jim
2011 G5 Deluxe
1999 Miata 10th Anniversary

barenekd

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Re: Piston Rings or Valve Job
« Reply #3 on: August 21, 2012, 11:36:53 PM »
If you can get an aircraft style that pumps air into the cylinder at a specific pressure (80 psi) You can tell how the compression is holding up. then you listen at the breather pipe (rings), exhaust pipe, (exhaust valve), and carb (intake valve) to determine what is leaking. Hard to do with a  standard compression gauge. As mentioned above, adding some oil and seeing the rise in compression is an indication the rings are leaking, but if it's the valves, you pretty much have to pull the head to determine the amount. But you were going to do that anyway, weren't you?
With 26,000 miles on it, you are due anyway!
Bare
2013 Moto Guzzi V7 Racer
2011 Black Classic G5 (RIP)
I refuse to tiptoe through life only to arrive safely at death
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BRADEY

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Re: Piston Rings or Valve Job
« Reply #4 on: August 22, 2012, 05:38:10 PM »
thanks everybody, now I guess its time to get back to work. I'll go by your advices and let you know how things transpire !

BRADEY

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Re: Piston Rings or Valve Job
« Reply #5 on: August 24, 2012, 04:09:02 PM »
Hi, I have put on a new filter and spark plug. Lowered the carb needle/ pin one notch (3rd groove from the top, as comes from factory) to lean out the mixture slightly. Did a short stint and all seems fine. Will do a proper 40-50 Miles ride and share more 8)

barenekd

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Re: Piston Rings or Valve Job
« Reply #6 on: August 24, 2012, 05:04:51 PM »
The bottom line is, if you're going to pull the top end off, you should do both a valve and ring job, especially with your mileage. Since the difference in labor difference for disassembly and assembly is minimal to pull the jug off, it's not very cost conscious to only do part of the job. If you only do one job, the other part will suffer and go away quicker.
Bare
2013 Moto Guzzi V7 Racer
2011 Black Classic G5 (RIP)
I refuse to tiptoe through life only to arrive safely at death
http://www.controllineplans.com

BRADEY

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Re: Piston Rings or Valve Job
« Reply #7 on: August 27, 2012, 06:58:00 AM »
Took her out on a long ride yesterday (530 kms). She performed very well for the first 100 kms, not like a new bike, but very well for her age and miles. I was able to hold her constantly above 80 KMPH with ease. When we stopped for breakfast, I checked the engine oil level and it was good. Then followed off road riding session in rain and the engine became rough, the torque was not available at the lower RPMs as in the morning. Second stop and the engine oil was 250 ml less than morning. None of the riders observed smoke from the exhaust, and yet the oil was disappering somewhere. In the evening we were back on the highway, and she was feeling better, but not as good as in the morning.........I guess an English lady would be easier to understand than the fickle nature of the Royal Enfield Bullet !!!!!!!